UICollectionViewCell中的UiviewControllers

我在UIViewController中有一个UICollectionView。collectionView包含一个故事板中的8个视图控制器标识符数组。数组中的每个视图控制器都从保存collectionView的UIViewController继承。

这是代码：

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return _contentPageRestorationIDs.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];

BaseContentViewController *contentViewController = (BaseContentViewController *)[self.storyboard instantiateViewControllerWithIdentifier:self.contentPageRestorationIDs[indexPath.row]];

// Set any data needed by the VC here
contentViewController.rootViewController = self;
contentViewController.view.frame = cell.bounds;
[cell addSubview:contentViewController.view];

return cell;
}

所以我的问题是我的收藏夹视图滑动性能确实很慢。如何提高UICollectionView的性能？不显示单元格内的视图控制器时，它们是否被“杀死”？

编辑：

根据这里的建议，我将数组更改为持有视图控制器，而不是标识符nsstring。

在ViewDidLoad中：

_collectionView.delegate=self;
_collectionView.dataSource=self;
PRzeroVC  *zeroVC    = [[PRzeroVC alloc]init];
PRoneVC   *oneVC     = [[PRoneVC alloc]init];
PRtwoVC   *twoVC     = [[PRtwoVC alloc]init];
PRthreeVC *threeVC   = [[PRthreeVC alloc]init];
PRfourVC  *fourVC    = [[PRfourVC alloc]init];
PRfiveVC  *fiveVC    = [[PRfiveVC alloc]init];

_base           = [[BaseContentViewController alloc]init];

_pages = [[NSArray alloc]initWithObjects:zeroVC,oneVC,twoVC,threeVC,fourVC,fiveVC, nil];

[_collectionView reloadData];



- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = (UICollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];

cell.layer.shouldRasterize = YES;
cell.layer.rasterizationScale = [UIScreen mainScreen].scale;
_base = (BaseContentViewController *)_pages[indexPath.row];

_base.rootViewController = self;
_base.view.frame = cell.bounds;
[cell addSubview:_base.view];

return cell;
}

我的单元格未显示视图知道为什么吗？